The MP for Birmingham Hodge Hill warned that Labour could not know what state the economy would be in by 2015, when it hopes to take power, and should not make any promises it could not be certain of keeping.

Speaking to the Birmingham Post during Labour’s conference in Manchester, he also warned that Labour was “on a journey” following its election defeat in 2010 and still had more to do to convince voters it could improve their lives.

Ed Balls, Labour’s shadow chancellor, disappointed some union leaders when he insisted during his conference speech that he could not promise to reverse any specific spending cuts or to undo the Governments’s public sector pay freeze.

Unison general secretary Dave Prentis said Mr Balls needed to show voters that “there is a real difference between Labour and the Tory party”.

He said: “To those who believe that driving down further the pay of public service workers will save jobs, I say you are wrong.”

But in a dig at Liberal Democrat leader Nick Clegg, Mr Byrne insisted: “What we’re not going to do is behave like Nick Clegg and make lots of promises that couldn’t be delivered in a month of Sundays.

“The reality is that the budget position is deteriorating so fast it’s impossible to know what kind of mess is going to be left by this government in two and a half years time.

“What Ed Balls is doing is the responsible thing in saying look, the books are getting worse and worse and worse, there is red ink all over the place, we are not going to make promises we can’t deliver and spending decisions are going to have to come closer to the next election.

“And if there is a Labour government re-elected in 2015, we are going to haver to look at every pound note government spends to figure out what we can do and what we can’t do. But we’re not going to pull the wool over people’s lives and we’re not going to make promises we can’t deliver.”

Labour was bouncing back after a massive election defeat in 2010, he said.

“We are on a journey and it was only two years ago that we polled one of the worst election defeats in our history and what a lot of people expected after that election defeat was that Labour would behave in the way it has in years gone by, which was to attack each other and fall out and actually we haven’t done that.

“We’ve gone straight back out there to reconnect with the public. I think we’re more united than we ever have been since I’ve been a member of Parliament.

“But it’s not the finished article.”

Mr Byrne warned that Labour would not allow the Conservative Party to “draw a line” under the behaviour of Birmingham MP Andrew Mitchell (Con Sutton Coldfield), who was reportedly rude to police officers guarding the gate to Downing Street, or Staffordshire MP Aidan Burley (Con Cannock Chase), who attended Nazi-themed stag party.

“I think Conservative MPs have behaved very badly. At worst they have betrayed what is behind the mask and I think Aidan Burley and Andrew Mitchell in different ways have revealed what many people fear about the true character of the Tory character, which is that they think there is one set of rules for them and another set of rules for everybody else.

“And most people I know in Birmingham don’t want people like that running the country.

“I think it’s deeply damaging for the Conservative Party and I think it has revealed the Prime Minister as a weak man because it has proved he cannot take tough decisions and sack Andrew Mitchell for what was a pretty nasty tirade.”

Earlier this year, Mr Byrne announced his intention to stand as mayor of Birmingham only for the city to vote against creating a mayor in a referendum.

He said he believed it was unlikely city voters would change their mind about wanting a mayor, and the battle now was to convince the Government to devolve more power to the city council as it was currently constituted.

“That is the battle we all have to throw ourselves into now. That’s the only game in town.”